2024年6月1日发(作者：)

表面光洁度表示符号（Surface finish is the symbol）

Surface finish is the old standard of surface roughness;

Their correspondence:

Surface finish level 14 = Ra 0.012

Surface finish level 13 = Ra 0.025

Surface finish level 12 = Ra 0.050

Surface finish level 11 = Ra 0.1

Surface finish level 10 = Ra 0.2

Surface finish level 9 = Ra 0.4

Surface finish level 8 = Ra 0.8

Surface finish level 7 = Ra 1.6

Surface finish level 6 = Ra 3.2

Surface finish level 5 = Ra 6.3

Surface finish 4 = Ra 12.5

Surface finish level 3 = Ra 25

Surface finish level 2 = Ra 50

Surface finish level 1 = Ra 100

Surface roughness units above is mu m, namely the micron = 10

^ 6 meters.

Surface roughness refers to the small spacing of the machining

surface and the unflatness of small peaks and valleys. The

distance between the two peaks or the trough (the wave length)

is small (below 1mm) and is indistinguishable from the naked

eye, so it is a microscopic geometry error. The smaller the

surface roughness, the smoother the surface. The size of

surface roughness has a great effect on the performance of

mechanical parts, mainly in the following aspects:

1) surface roughness affects wear resistance of parts. The

rougher the surface, the smaller the effective contact area

between the surface, the greater the pressure, the faster the

wear.

2) the surface roughness affects the stability of the matching

property. The rougher the surface, the more likely it is to wear

out, increasing the gap in the working process. In the case of

overturning, the joint strength is reduced by squeezing the

micro-convex peak and reducing the actual effective overgain.

3) the surface roughness affects the fatigue strength of the

parts. The surface of rough parts has large trough, they are

like sharp Angle gap and crack, they are sensitive to stress

concentration, thus affecting the fatigue strength of the

parts.